Purging and drying system for gas blast circuit interrupiers

ABSTRACT

A dry nitrogen gas is forced through the high and low-pressure system and the gas filled bushings of a high voltage SF6 blast circuit interrupter to purge the system of moisture before filling the system with SF6. Heat is applied to the various components during the purging operation.

D United States Patent A 1 3,602,669

[72] Inventors Henry G. Meier [56] References Cited f f Ch d B b k UNITED STATES PATENTS c u a 991,483 5/1911 Creighton 200/148 E 3 214 546 10/1965 Leeds 200/148 E [21] Appl. No. 20,607 [22] Filed Mar. 8,1970 3,390,241 6/1968 Frowenn 200/148 E 451 Patented Aug. 31, 1971 FOREIGN PATENTS [73] Assignee I-T E Imperial Corporation 625,831 '8/1961 Canada 200/148 G Philadelphia Primary Examiner- Robert S. Macon Alt0rney Ostrolenk', Faber, Gerb and Soffen [54] PURGING AND DRYING SYSTEM FOR GAS BLAST CIRCUIT INTERRUP'IERS 9 Claims, 3 Drawing Figs. [52] US. Cl .0. ZOO/148E, ABSTRACT: A dry nitrogen gasis forced through the high 200/ 148 B, 174/14 and low-pressure system and the gas filled bushings of a high [51] Int.Cl. ..H01h33/54 voltage SF blast circuit interrupter to purge the system of [50] Field of Search 200/148 B, moisture before filling the system with SP Heat is applied to 148 E, 148 G, 148 R; 174/14, l5, l6

the various components during the purging operation.

RELATED APPLICATIONS The present application is for use with SF circuit breakers of the type shown in copending application Ser. No. 680,778, filed Nov. 6, 1967, in the name of John H. Golota. The invention also uses a modified bushing structure based on the bushing of the type shown in copending application Ser. No. 852,534, filed Aug. 25, 1969, in the name of James R. Mc- Cloud. Both of the above applications are assigned to the assignee of the present invention.

BACKGROUND OF THE INVENTION SUMMARY OF THE INVENTION In accordance with the invention, a dry nitrogen gas is injected into the high-pressure input lines of the system and is discharged from the end of the low-pressure system. In addition, the gas is purged through an opening in the flange of the insulator bushings, which are also to be filled with SP so that a path is formed for the fiow of purging gas through its bushing. At the time the purging gas flows, heat is added to the breaker tanks by their normally present resistance heaters, and by batteries of radiant energy heaters which may be directed at the various tanks.

BRIEF DESCRIPTION OF THE DRAWINGS F l6. 1 schematically shows the purging system of the invention in connection with a schematically shown SP gas interrupter.

FIG. 2 shows, in cross section, a gas filled insulation bushing which may be used for the circuit breaker of FIG. 1.

FIG. 3 shows, in cross section, the manner in which the flange of the bushing of FIG. 2 can be modified to permit purging of the bushing by permitting purging gas to flow through the bushing flange to external atmosphere.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT Referring first to FIG. 1, there is shown, in schematic form, a high voltage, sulfur hexafluoride gas circuit breaker and the gas supply system therefor. In the gas pressure system, the heavy lines represent high-pressure conduits, while the thinner lines represent low-pressure conduits.

The circuit breaker which is shown in detail in copending application Ser. No. 680,778 consists of a low-pressure tank 20 which contains two series connected interrupter structures 21 and 22 which are respectively connected to terminal bushings 23 and 24. Each of interrupter structures 21 and 22 contain a pan of separable contacts and a so-called blast valve. The opening of the contacts is associated with the brief opening of the blast valves so that high-pressure SF will flow through the separating contacts to extinguish the are drawn between the contacts. The high-pressure gas is provided from high-pressure tanks 25 and 26 which are connected to inter rupter 21 and 22, as shown by high-pressure conduits 27 and 28, respectively. Note that a local reservoir of high-pressure gas may be contained within interrupters 21 and 22. Note further that the blast valve of the interrupters serves as the barrier between the high-pressure at conduits 27 and 28 and the low-pressure of the interior of tank 20.

The SE, in high-pressure tanks 25 and 26 is held at a given high-pressure by a suitably controlledcompressor 30 which is connected to high-pressure conduit 31 through oil trap 32, oil filter 33 and check valve 34. High-pressure conduit 31 is then connected to a control valve system including valves 41, 42, 43, 44 and 45. When the circuit breaker is in service, valves 42 and 44 are open and valves 41, 43 and 45 are closed. Highpressure conduit 31 is then connected, through valve 42, to high-pressure conduits 50 and 51 and thus to tanks 25 and 26.

The low-pressure return system from tank 20 consists of conduit 55, valve 44 and conduit 56. Conduit 56 is then connected to the input compressor 30, through the filter-drier 57.

Heaters, such as resistance heaters 60, 61 and 62, 63 are provided for tanks 25 and 26 in the manner shown in copending application Ser. No. 845,376, filed July 28, 1969, in the name of Meier and DeSeve. These heaters insure that the high-pressure SF gas will be heated above its liquefaction temperature. A hygrometer 65 is then suitably connected to the system, as by the schematically illustrated coupling 66.

In accordance with the invention, a connection 70 is pro vided in conduit 71 for coupling to a source of dry gas for purging the system before filling with SF and a second connection 72 is provided for removal of the purge gas. The connections 70 and 72 can be openings having suitable removable plugs.

In order to dry the system shown in FIG. 1, valve 41 is opened so that connection 70 is connected to the high-pressure side of the system. The blast valves of interrupters 21 and 22 are then opened in a suitable manner, and are held in the open position. A source of dry gas, such as nitrogen, is then connected to connection 70, and dry gas flows through the system and around the path indicated by the arrows in FIG. I includingcomponents 41, 42, 50, 25-26, 27-28, 21-22, 20, 55, 44 and 72 where the purge gas is discharged. This purge is continued until a sufficient low moisture level, for example, 150 parts per million, is measured by hygrometer 65. Note that moisture level can also be measured at the purge gas outlet 72.

The drying process is accelerated by applying heat to the tanks of the circuit breaker system. This may be done by energizing the available heaters 60 to 63 ing added heater elements to the exteriors of tanks 20, 25 and 26. Batteries of infrared lamps, shining on the tank exteriors, are of advantage. 7 V 3 To accelerate the drying process, a vacuum (about 1 mm. mercury) is drawn in the breaker thereto. The tanks are then refilled with new purging gas, thus ensuring that the purging gas will be renewed in all parts of the breaker, even in areas where the flow-through purging method described above would not be fully effective. The drawing of a vacuum and refilling with purge gas can be repeated as many times as necessary. The changeover from the flow-through method to the vacuum method or from the vacuum method to the flow-through method is accomplished by changing valve positions. Thus, valve 45 is closed, and valve 46 is open for the flow-through method. Both valves 45 and 46 are open and purge connection 72 and purge outlets and 86 are closed off for the vacuum method.

Once the moisture level has been sufficiently reduced, dry gas can be circulated through the driers and filters 57 and 33 and through the breaker. The valves 43, 45, and 46, the purge connection 72 and the purge gas outlets 85 and 86 in the bushings will be closed; the valves 42 and 44 will be opened. Withthe compressor 30 operating, the circulating gas, for instance, nitrogen, will be forced to fiow through the driers and filters which will reduce the moisture level still lower; for example, ,to 40 parts per million. This same circulating process can be applied after the breaker has been filled with SF,,, whereby the SF., gas is used to purge the system.

As an important feature of the invention, and when the insulation bushings 23 and 24 are filtered with SF gas, delivered and, if desired, by providtanks while applying heat from the high-pressure tanks 25 and 26, the bushings are provided with gas discharge openings to permit flow of purging gas through and out of the bushings to the external atmosphere. Thus, in FIG. 1 each of bushings 23 and 24 are schematically illustrated as having hollow, central conductors 80 and 81, surrounded by insulating shells 82 and 83, respectively. The space between the central conductors 23 and 24 and the shells 82 and 83, respectively, is to be filled with SF and, therefore, should be completely dried before filling with SP In accordance with the invention, the mounting flanges of bushings 23 and 24 are provided with purge outlet connections 85 and 86 through which dry purge gas flowing from input connection 70 can flow up the interior of conductors 80 and 81 and within shells 82 and 83, thereby to dry the bushing spaces.

FIG. 2 shows, in cross section, a typical bushing which can be modified to have a purge gas outlet in its mounting structure to serve the purpose of bushings 23 and 24 of FIG. 1, and is of the type described in copending application Ser. No. 852,534.

Referring to FIG. 2, the bushing consists of two insulator columns 110 and 111 which may be of any standard configuration and which are joined in end-to-end relation through an annular mounting flange 112. The annular mounting flange 112 is of the standard type and contains numerous bolt hole openings, such as bolt holes 113 and 114, such that the insulator can be mounted to any suitable enclosure such as the fragmentarily shown enclosure 135 which could, for example, represent the housing 20 of FIG. 1.

Relatively hard, load-supporting gaskets 116 and 140 are provided between the flange plates 112 and 132 and insulator section 111 to protect the insulator from damage by coming into contact with these metal plates.

The insulation section 110 is above the exterior of the tank 115 so that a good seal must be provided between the flange plate 112 and'insulator 110. This seal is shown in FIG. 2 as a relatively hard, load-supporting compression gasket 120 contained within suitable soft, sealing stop gaskets 121 and 122. The insulator bushing of FIG. 2 then contains a main elongated conductor 130 (similar to the conductors 80 and 81 in FIG. 1) which is threaded into a conductive adapter 131 which is received bythe conductive head plate 132. The interrupter within the housing 1 which is to be connected to conductor 130 is connected thereto through a suitable threaded connection, for example, with the adapter 131.

The conductive tube 130 is open at its bottom so that purge gas can enter the interior of the bushing.

Conductive plate 132 is also provided with an opening 136, which is covered by a filter 137, as shown in FIG. 2, where filter 137 is held in place by screw 138 and gasket 139. This structure is useful for removing condensed moisture from the inside of the bushing.

The outer end of the insulation bushing, as shown in the upper part of FIG. 2, contains a well-contoured conductive end plate 141 which has a threaded terminal 142 extending therefrom so that convenient connection may be made to the bushing. Conductive member 141 is then sealed to the upper end of hollow insulator section 110 by a good pressure seal consisting of the hard, load-bearing compression gasket 143 and its relatively soft, sealing stop gaskets 144 and 145. The upper end of conductor 130 is spaced from conductive member 141 so that the conductor 130 may expand and contract at a different rate than insulator sections 110 and 111,

due to temperature change.

Electrical connection between conductive member 141 and the central conductor 130 and the means for holding the insulator assembled include a spring-receiving disc 150 and a conrespect to conductor after the bushing has been assem bled.

Electrical connection is made between conductive member and flange plate 151 and thus conductor 130 by means of flexible, conductive straps. These flexible, conductive straps may be packages of thin, copper sheets,,for example, 25 layers of copper sheets, each having a thickness of 0.010 inches. A typical flexible conductor of this type is shown in FIG. 2 as flexible conductive member 160. A plurality of such flexible members will be distributed around the periphery of flange member 151.

One end of the conductive members, such as conductive member 160, is bolted to the interior of conductive member 141 as by the bolt-161, while the other end envelopes around the exterior of the flange as shown, and is disposed beneath a pressure washer 162. Conductive member may have an opening therethrough for passing a threaded insulated shank 163 which serves as a spring guide for the parallel springs 164 and 165. One end of springs 164 and 165 bear on pressure washer 162 in order to make good electrical contact between conductor 160 and flange 151. The other end of springs 164 and 165 rest on insulated washers 166 which are carried on disc 150 as shown. Note that items 163-166 and are insulated to prevent the various springs and bolts from carrying current and sparking to parts 150 and 151.

Spring-receiving disc 160 is then rigidly threaded into engagement with conductive member 141 as by insulated bolts such as bolt 180. Note that bolt 180, along with seven other bolts in the preferred embodiment of the invention, will also pass through aligned openings in flange member 151.

Springs 164 and 165 hold the entire insulator bushing in mechanical alignment, with the insulator sections 110 and 111 being in compression. That is, springs 164 and 165 are compression springs which urge members 150 and 151 away from one another. This has the effect of pressing conductive end members 141 and 132 toward one another, thereby applying forces tending to hold the bushing assembled and applying pressure to the various seals throughout the assembly. At the same time, a strong pressure connection is made between flexible conductive strap 160 and the flange .151 to establish a good path for electrical current from conductive member 141 through the flexible conductors to conductive flange 151 and thence through conductor 130 to the adapter 131.

If there are dimensional changes of conductor 130 with respect to the insulator housings 110 and 111, these dimensiorial changes will be easily absorbed by the flexible conductors, such as conductor 160, without cracking the insulators, while a good pressure seal is maintained. throughout the interior of the insulator for those portions of the insulator bushing which are above the housing 115.

To modify the bushing of FIG. 2 for use in accordance with the arrangement of FIG. 1, an opening is formed in flange 112. Thus, as shown in FIG. 3, flange 112 is provided with an opening 190. Opening communicates with'a purge outlet opening 191 which can be plugged by a threaded plug 192. A bronze filter screen 193 is held on a seal ring 194 and over the opening 190 by spring 195. Note that opening 191 and plug 192 correspond to connections 85 or 86 in FIG. 1. r

In operation, and during the purging, plug 192 is removed. Dry nitrogen is then flushed through the breaker and into the bushing through the conductive tube 130, open at the bottom as shown in FIG. 2. Thus, some nitrogen flows up rod 130 and then down the interior volume of shell 110, and out opening 190. Another portion of the purging gas flows through opening 136, through shell 111, and out opening 190. Therefore. there is a thorough purge of moisture from the bushing.

Althoughthis invention has been described with respect to particular embodiments, it should be understood that many variations and modifications will now be obvious to those skilled in the art, and, therefore, the scope of this invention is limited not by the specific disclosure herein, but only by the appended claims.

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

' l. A gas control and purging system for a high voltage gas circuit breaker; said high voltage gas circuit breaker including a high-pressure chamber, a low-pressure chamber, and an interrupter disposed within said low-pressure chamber; said gas control system including high-pressure conduit means connected to said high-pressure chamber, low-pressure conduit means connected to said low-pressure chamber, valve means connected in said interrupter for permitting communication between said high and low-pressure chambers, and compressor means connected between said high and low-pressure conduit means for establishing a pressure differential therebetween; said purging system including first connection means in said high-pressure conduit for connection to a source of dry purging gas, and second connection means in said lowpressure conduit for exhausting purging gas to the external atmosphere; said purging gas flowing serially through at least portions 'of said high-pressure conduit means, said high-pressure chamber, said interrupter, said low-pressure chamber and at least portions of said low-pressure conduits; said high voltage gas circuit breaker being adapted to be filled with sulfur hexafluoride after said system is purged of moisture; said purging gas having substantially no moisture content.

2. The system of claim 1 which further includes heater means connected to said high and low-pressure chambers.

3. The system of claim 2 which includes a hygrometer connected to said system; said system being purged until the moisture therein is reduced to below 150 parts per million, as indicated by said hygrometer.

4. A gas control and purging system for a high voltage gas circuit breaker; said high voltage gas circuit breaker including a highpressure chamber, a low-pressure chamber, and an interrupter disposed within said low-pressure chamber; said gas control system including high-pressure conduit means connected to said high-pressure chamber, low-pressure conduit means connected to said low-pressure chamber, valve means connected in said interrupter for permitting communication between said high and low-pressure chambers, and compressor means connected between said highand low-pressure conduit means for establishing a pressure differential therebetween; said purging system including first connection means in said high-pressure conduit for connection to a source of dry purging gas, and second connection means in said lowpressure conduit for exhausting purging gas to the external atmosphere; said purging gas flowing serially through at least portions of .said high-pressure conduit means, said high-pressure chamber, said interrupter, said low-pressure chamber and at least portions of said low-pressure conduits; said high voltage gas circuit breaker being adapted to be filled with sulfur hexafluoride after said system is purged of moisture; said purging gas having substantially no moisture content; said circuit breaker further including an insulator bushing extending through said low-pressure chamber and connected at one end thereof to said interrupter; said insulator bushing having a central conductor, an insulation shell spaced from and surrounding said central conductor; the volume between said central conductor and said insulation shell communicating with said low-pressure chamber; a portion of said insulator bushing being disposed externally of said low-pressure chamber; and a third connector means including an opening through said insulator bushing at the said external portion thereof for conducting portions of said purging gas through the interior volume of said insulator bushing to the external atmosphere.

5. The system of claim 4 wherein said insulator bushing has a mounting flange for mounting said bushing on said low-pressure chamber; said mounting flange being disposed on the exterior of said low-pressure chamber; said opening through said insulator bushing being formed through said mounting flange.

6. The system of claim 5 which further includes heater means connected to said high and low-pressure chambers.

7. The system of claim 5 which includes'a hygrometer connected to said system; said system being purged until the moisture therein is reduced to below parts per million, as

indicated by said h grometer.

8. The system 0 claim 5 wherein said central conductor is hollow and forms a gas channel to the outer end of said insula' tor bushing and to the top of the interior volume of said bushing; the lower end of said central conductor communicating with said low-pressure chamber; the bottom of said insulator bushing containing openings therethrough in direct communication with said low-pressure chamber, whereby, during purging, purging gas flows into said interior volume from the top and bottom thereof.

9. The system of claim 8 wherein said mounting flange is generally centrally located along the length of said bushing. 

1. A gas control and purging system for a high voltage gas circuit breaker; said high voltage gas circuit breaker including a high-pressure chamber, a low-pressure chamber, and an interrupter disposed within said low-pressure chamber; said gas control system including high-pressure conduit means connected to said high-pressure chamber, low-pressure conduit means connected to said low-pressure chamber, valve means connected in said interrupter for permitting communication between said high and low-pressure chambers, and compressor means connected between said high and low-pressure conduit means for establishing a pressure differential therebetween; said purging system including first connection means in said high-pressure conduit for connection to a source of dry purging gas, and second connection means in said low-pressure conduit for exhausting purging gas to the external atmosphere; said purging gas flowing serially through at least portions of said high-pressure conduit means, said high-pressure chamber, said interrupter, said low-pressure chamber and at least portions of said low-pressure conduits; said high voltage gas circuit breaker being adapted to be filled with sulfur hexafluoride after said system is purged of moisture; said purging gas having substantially no moisture content.
 2. The system of claim 1 which further includes heater means connected to said high and low-pressure chambers.
 3. The system of claim 2 which includes a hygrometer connected to said system; said system being purged until the moisture therein is reduced to below 150 parts per million, as indicated by said hygrometer.
 4. A gas control and purging system for a high voltage gas circuit breaker; said high voltage gas circuit breaker including a high-pressure chamber, a low-pressure chamber, and an interrupter disposed within said low-pressure chamber; said gas control system including high-pressure conduit means connected to said high-pressure chamber, low-pressure conduit means connected to said low-pressure chamber, valve means connected in said interrupter for permitting communication between said high and low-pressure chambers, and compressor means connected between said high- and low-pressure conduit means for establishing a pressure differential therebetween; said purging system including first connection means in said high-pressure conduit for connection to a source of dry purging gas, and second connection means in said low-pressure conduit for exhausting purging gas to the external atmosphere; said purging gas flowing serially through at least portions of said high-pressure conduit means, said high-pressure chamber, said interrupter, said low-pressure chamber and at least portions of said low-pressure Conduits; said high voltage gas circuit breaker being adapted to be filled with sulfur hexafluoride after said system is purged of moisture; said purging gas having substantially no moisture content; said circuit breaker further including an insulator bushing extending through said low-pressure chamber and connected at one end thereof to said interrupter; said insulator bushing having a central conductor, an insulation shell spaced from and surrounding said central conductor; the volume between said central conductor and said insulation shell communicating with said low-pressure chamber; a portion of said insulator bushing being disposed externally of said low-pressure chamber; and a third connector means including an opening through said insulator bushing at the said external portion thereof for conducting portions of said purging gas through the interior volume of said insulator bushing to the external atmosphere.
 5. The system of claim 4 wherein said insulator bushing has a mounting flange for mounting said bushing on said low-pressure chamber; said mounting flange being disposed on the exterior of said low-pressure chamber; said opening through said insulator bushing being formed through said mounting flange.
 6. The system of claim 5 which further includes heater means connected to said high and low-pressure chambers.
 7. The system of claim 5 which includes a hygrometer connected to said system; said system being purged until the moisture therein is reduced to below 150 parts per million, as indicated by said hygrometer.
 8. The system of claim 5 wherein said central conductor is hollow and forms a gas channel to the outer end of said insulator bushing and to the top of the interior volume of said bushing; the lower end of said central conductor communicating with said low-pressure chamber; the bottom of said insulator bushing containing openings therethrough in direct communication with said low-pressure chamber, whereby, during purging, purging gas flows into said interior volume from the top and bottom thereof.
 9. The system of claim 8 wherein said mounting flange is generally centrally located along the length of said bushing. 